CEA Levels and Colon Cancer

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Dear OncoLink "Ask the Experts,"
What is a CEA test, how accurate or dependable is it?

Timothy C. Hoops, MD, Clinical Assistant Professor of Medicine in the Gastroenterology Division at the University of Pennsylvania and Director of Gastroenterology at Penn Medicine at Radnor, responds:

Carcinoembryonic antigen or CEA is a glycoprotein that is present in many tissues including the cells that line the colon. Since colon cancers develop from these cells, one can find elevated CEA levels in the blood of patients that have colon cancer. It can also rise with other cancers.

The most common use for measuring CEA levels is to look for recurrence of colon cancer after treatment for cure. If there is an elevated CEA prior to surgery, it will usually return to normal if the entire tumor has been removed. Subsequent monitoring may signal a recurrence of the cancer. The CEA test has been promoted as a way to detect a recurrence before it is clinically apparent, allowing earlier, and hopefully more effective retreatment. Unfortunately, some colon cancers do not present with elevated CEA levels, which makes it a less than perfect test.

The other proposed use of the CEA level is to screen for colon cancer. Unfortunately, levels are uncommonly elevated, especially with small early cancers, resulting in a high false-negative rate. Additionally, it can be mildly elevated in smokers or in other cancers, resulting in a high false positive rate. Between these false-positive and false-negative tests, it is too unreliable as a test to screen for colon cancer.